Active and Passive attacks in Information Security
Last Updated : 9 Jan, 2026
Active and Passive attacks are two major categories of cybersecurity threats in information security, where active attacks disrupt or modify systems, while passive attacks secretly monitor and collect information.
Cyber attacks are broadly classified into Active and Passive attacks
Active attacks directly alter data, systems, or network operations
Passive attacks focus on eavesdropping and information gathering without modification
Active attacks affect integrity and availability, while passive attacks target confidentiality
Understanding both helps in designing effective security measures
What is a Cyber Attack?
A cyber attack is a deliberate attempt to gain unauthorized access to computer systems or networks in order to steal data, disrupt operations, or cause damage to digital resources.
Targets individuals, organizations, or government systems
Aims to steal information, disrupt services, or cause financial and reputational damage
Common types include malware, phishing, denial-of-service (DoS), and man-in-the-middle (MitM) attacks
Can lead to data breaches, system downtime, and financial loss
Awareness and security measures help protect digital assets and personal information
Classification of Cyber Attacks
Cyber attacks are mainly divided into two categories:
Active Attacks
Passive Attacks
Sometimes, attackers combine both techniques to increase the impact of the attack.
Active Attacks
An active attack is one in which the attacker directly interacts with the target system to modify, disrupt, or destroy data or services. These attacks are easier to detect because they affect system operations.
A masquerade attack is a cyber attack in which an attacker impersonates a legitimate user or system to gain unauthorized access to data, systems, or restricted resources by deceiving others into sharing sensitive information.
There are several types of masquerading attacks, including:
Username and Password Masquerade: In this masquerade attack, a person uses either stolen or even forged credentials to authenticate themselves as a valid user while gaining access to the system or application.
IP address masquerade: This is an attack where the IP address of a malicious user is spoofed or forged such that the source from which the system or the application is accessed appears to be trusted.
Website masquerade: A hacker creates a fake website that resembles as a legitimate one in order to gain user information or even download malware.
Email masquerade: This is an e-mail masquerade attack through which an attacker sends an apparently trusted source email so that the recipient can mistakely share sensitive information or download malware.
Repudiation attacks are a type of cyber attack wherein some person does something damaging online, such as a financial transaction or sends a message one does not want to send, then denies having done it.
There are several types of repudiation attacks, including:
Message repudiation attacks: In this attack, a message has been sent by an attacker, but the attacker later denies the sending of the message. This can be achieved either through spoofed or modified headers or even by exploiting vulnerabilities in the messaging system.
Transaction repudiation attacks: Here, in this type of attack, a transaction-for example, monetary transaction-is made, and at after some time when the evidence regarding the same is being asked to be give then the attacker denies ever performing that particular transaction.
Data repudiation attacks: In a data repudiation attack, data is changed or deleted. Then an attacker will later pretend he has never done this. This can be done by exploiting vulnerabilities in the data storage system or by using stolen or falsified credentials.
4. Replay
It is a passive capturing of a message with an objective to transmit it for the production of an authorized effect.
In this type of attack, the main objective of an attacker is saving a copy of the data that was originally present on that particular network and later on uses it for personal uses.
Once the data gets corrupted or leaked it becomes an insecure and unsafe tool for its users.
Impact: Unauthorized access, session hijacking, data misuse
A passive attack involves monitoring or eavesdropping on communications without modifying data. These attacks are difficult to detect because they do not affect system operations.
Characteristics of Passive Attacks
No modification of data
Focus on information gathering
Hard to detect
Target confidentiality rather than availability or integrity
Types of Passive Attacks
Below are the two types of Passive Attacks:
1. The Release of Message Content
Telephonic conversation, an electronic mail message, or a transferred file may contain sensitive or confidential information. We would like to prevent an opponent from learning the contents of these transmissions.
Suppose that we had a way of masking (encryption) information, so that the attacker even if captured the message could not extract any information from the message.
The opponent could determine the location and identity of communicating host and could observe the frequency and length of messages being exchanged.
This information might be useful in guessing the nature of the communication that was taking place.
The most useful protection against traffic analysis is encryption of SIP traffic.
To do this, an attacker would have to access the SIP proxy (or its call log) to determine who made the call.
